Preheat a conventional oven to 350°F and set an oven rack in the center of the oven. Grease a 9" x 13" x 2" baking pan. Combine the sugars, spices, baking soda, and salt in a mixing bowl. Add the butter, eggs, and vanilla and beat on medium-high until light and fluffy, about 2 minutes. Scrape the bowl and add the flour, oats, coconut, cranberries, and walnuts, beating on low speed for about 20-30 seconds until the mixture is evenly blended and holds together. Bake in the preheated oven 25-30 minutes. When done the cake will be golden brown, but the center will still be a little soft. Do not over bake. Remove the pan from the oven and set on a wire rack to cool. While the cake is cooling, mix the icing.
Mix the confectioner's sugar and 1 T of the cream using a small whisk. Add just enough of the remaining cream to make a consistency that will drizzle easily, but not be runny. Drizzle the icing generously over the completely cooled cake and sprinkle with colored jimmies. Let the icing set, and double wrap tightly with plastic wrap. Store at room temperature for up to 4 days. 2 dozen.
Chef's Note: These chewy, old-fashioned bars are mildly spiced and filled with just the right amount of nuts and fruit. The colored jimmies are optional, but add a festive touch for the holidays.